diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2019-04-09 14:28:23 +0200 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2019-05-10 10:53:21 +0100 |
| commit | 993ed89f35bf2b2250727667f2a640b3c232259f (patch) | |
| tree | f53e1f9d206d95153bde411252cb2f23617fa919 /util | |
| parent | 118f99442d3a8ce47836978cddd9206ac2d2b001 (diff) | |
| download | qemu-993ed89f35bf2b2250727667f2a640b3c232259f.zip | |
aio-posix: ensure poll mode is left when aio_notify is called
With aio=thread, adaptive polling makes latency worse rather than
better, because it delays the execution of the ThreadPool's
completion bottom half.
event_notifier_poll() does run while polling, detecting that
a bottom half was scheduled by a worker thread, but because
ctx->notifier is explicitly ignored in run_poll_handlers_once(),
scheduling the BH does not count as making progress and
run_poll_handlers() keeps running. Fix this by recomputing
the deadline after *timeout could have changed.
With this change, ThreadPool still cannot participate in polling
but at least it does not suffer from extra latency.
Reported-by: Sergio Lopez <slp@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 20190409122823.12416-1-pbonzini@redhat.com
Cc: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1553692145-86728-1-git-send-email-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20190409122823.12416-1-pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'util')
| -rw-r--r-- | util/aio-posix.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/util/aio-posix.c b/util/aio-posix.c index 6fbfa7924f..db11021287 100644 --- a/util/aio-posix.c +++ b/util/aio-posix.c @@ -519,6 +519,10 @@ static bool run_poll_handlers_once(AioContext *ctx, int64_t *timeout) if (!node->deleted && node->io_poll && aio_node_check(ctx, node->is_external) && node->io_poll(node->opaque)) { + /* + * Polling was successful, exit try_poll_mode immediately + * to adjust the next polling time. + */ *timeout = 0; if (node->opaque != &ctx->notifier) { progress = true; @@ -558,8 +562,9 @@ static bool run_poll_handlers(AioContext *ctx, int64_t max_ns, int64_t *timeout) do { progress = run_poll_handlers_once(ctx, timeout); elapsed_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - start_time; - } while (!progress && elapsed_time < max_ns - && !atomic_read(&ctx->poll_disable_cnt)); + max_ns = qemu_soonest_timeout(*timeout, max_ns); + assert(!(max_ns && progress)); + } while (elapsed_time < max_ns && !atomic_read(&ctx->poll_disable_cnt)); /* If time has passed with no successful polling, adjust *timeout to * keep the same ending time. @@ -585,8 +590,7 @@ static bool run_poll_handlers(AioContext *ctx, int64_t max_ns, int64_t *timeout) */ static bool try_poll_mode(AioContext *ctx, int64_t *timeout) { - /* See qemu_soonest_timeout() uint64_t hack */ - int64_t max_ns = MIN((uint64_t)*timeout, (uint64_t)ctx->poll_ns); + int64_t max_ns = qemu_soonest_timeout(*timeout, ctx->poll_ns); if (max_ns && !atomic_read(&ctx->poll_disable_cnt)) { poll_set_started(ctx, true); |